1. Field of the Invention
The present invention relates to a supply circuit of a clock signal in, for example, a computer.
2. Description of the Related Art
FIG. 4 shows a conventional clock signal supply circuit 1. A clock signal outputted from a clock signal generator 35 is supplied to circuit units provided in the inside of a personal computer (called pasokon), such as a CPU 31, a memory 32, a video card 33, and a sound card 34. The clock signal generator 35 outputs a rectangular wave, and is mounted on a mother board 36 in the personal computer as shown in FIG. 5.
The CPU 31 or the memory 32 is constructed as an integrated circuit, and is mounted on the mother board 36. Besides, the video card 33 or the sound card 34 is made of a dedicated card-type board on which an image processing circuit or a sound processing circuit is constructed. Connectors 37 are attached on the mother board 36, and these cards are mounted to the mother board 36 through the connectors 37.
A wiring conductor (not shown), which becomes a bus, is formed on the mother board 36, and the clock signal is supplied to the respective circuit devices through this wiring conductor.
In the conventional structure, the clock signal is transmitted on the mother board and is inputted to the respective circuit devices. The rectangular wave includes many higher harmonics as is generally known, and as shown in FIG. 6, the levels of odd harmonics are especially high. Thus, they easily leak out of the personal computer, and there has been a problem that they interfere with other electronic equipment.
The invention has an object to realize a circuit for preventing odd harmonics of a clock signal from leaking out of an equipment, such as a personal computer, using the clock signal.
To the above problem, a circuit of the invention includes a sine wave oscillator and a circuit operating with an oscillation signal, as a clock signal, outputted from the sine wave oscillator, and is characterized in that a waveform shaping circuit is provided correspondingly to the circuit, the circuit and the waveform shaping circuit are constructed in a same circuit unit, and the oscillation signal is converted into a rectangular wave by the waveform shaping circuit in the circuit unit and is supplied to the circuit.
Besides, a feature is that the circuit unit is an integrated circuit constituting a circuit such as a CPU or a memory.
Besides, a feature is that the circuit unit is a dedicated card-type board constituting a circuit such as a sound processing circuit or an image processing circuit.
Besides, a feature is that the sine wave oscillator is constituted by a PLL synthesizer.